U.S. takes aim at the ISIS oil business

Think of ISIS as an oil company under serious stress.

The United States claims it has severely hit the Islamic State's ability to profit from oil, which has fueled maybe half of its terrorism operations in 2015.

Earlier this year, ISIS was making $40 million every month on oil alone, according to the U.S. Treasury. Then came a constant, targeted bombing campaign. Now ISIS is making only a fraction of that, according to a senior state department official.

American officials say it's too early to tell exactly how much damage has been done.

The Paris attacks happened on November 13, and since the Tuesday after that, airstrikes by the U.S.-led coalition have intensified. According to White House security advisers, coalition bombs have blown up 283 oil tanker trucks, 120 storage tanks, and "a significant amount" of oil field equipment in eastern Syria.

"We're already seeing a very significant slowdown in the operation," the senior State Department official said at a recent press briefing. "There is still a functioning capability, but without a doubt, it's under strain."

The bombings against ISIS are being carried out by planes like this U.S. Air Force F-15E Strike Eagle, which just landed at Incirlik Air Base in Turkey on Nov. 12.

America's strategy against ISIS oil

Oil needs to be pulled from the ground, then refined into higher quality petroleum products. That entire process is under attack.

At first, U.S.-led bombings slowed down production. Bombers took out industrial refineries. This forced ISIS militants to rely on "primitive refining techniques" to refine it, like burning crude oil in open pits, according to the Financial Action Task Force, which tracks terrorist financing. The State Department official said it was a strategy intended on "moving the operation from a 20th Century operation to a 17th Century operation."

U.S.-led coalition bombings are forcing ISIS to distill crude oil in simple pits, as this Syrian man did outside Raqqa in 2013.

Then the American military moved on to disrupt the ISIS oil supply chain. American and coalition bombers have targeted the long lines of massive trucks that form on the roads leading to ISIS-controlled oil fields.

Truckers are now scared to line up to buy oil.

As a result, ISIS is producing oil that's less refined -- and at a slower pace. This oil fetches a lower price on the black market and takes longer to get to market -- starving ISIS of cash.

Over the last few weeks, the coalition has stepped up attacks on "strategic equipment."

"We will continue to strike ISIL's oil infrastructure and put sustained pressure on this resource that's very important to them," Lieutenant Commander Ben Tisdale, a U.S. Navy spokesman, told CNNMoney.

The countries taking part in the airstrikes are Australia, Bahrain, Belgium, Canada, Denmark, France, Jordan, the Netherlands, Saudi Arabia, Turkey, the United Arab Emirates, as well as the British and Americans.

The United States has conducted 78% of the 8,783 bombings, according to the latest Defense Department records.

There's another force at work hurting ISIS's oil revenue. Rock-bottom oil prices have also reduced what ISIS can fetch on the black market. In the past, ISIS has sold oil at a 25% to 50% discount. Right now, oil is diving below $38 a barrel, the lowest level in 7 years. ISIS has to sell it even cheaper than that.

ISIS claims it gained control of this gas field in central Syria near the city of Palmyra.